John Pearson, one of the four prosecutors in the case, said the accused were prone to "unjustified acts of physical violence against people who were in their custody."
The Crown's first witness, Christopher Quigley, told the court he was assaulted by one of the accused while another looked on.
"I was attacked by officers while I was in custody," he said. " I was beaten repeatedly."
Quigley, a marijuana dealer, said he was arrested by plainclothes officers over a pair of stolen sunglasses and taken to the station, where he was asked by increasingly angry officers where he kept his drugs and money.
Photographs introduced as evidence show cuts and bruises on Quigley's face and body, including a bruised rib and a black eye that swelled shut.
He took the photographs, Quigley said, "to document what happened to me while in police custody."
Quigley will continue his testimony Tuesday, but Pearson alleged in his opening statement that Quigley was "repeatedly assaulted over his nine-hour detention to the point of unconsciousness."
The officers also searched the home of Quigley's then-60-year-old mother and convinced her to hand over the key to a safe deposit box, where she said she was holding some cash for her son, Pearson told the court as he laid out the case he intends to prove over the lengthy trial.
Out of the $54,000 Quigley had said was in the safety deposit box, only $22,850 was logged in by the officers and eventually returned, Pearson told the court.
The Crown alleges the investigation into Quigley, as well as four others, included illegal searches and search warrants, as well as falsified notes and records to cover them up.
In the case of another suspect arrested over a cocaine deal, there was a discrepancy of about $1,400 between the amount of money the man said he had on him when he was arrested and what one of the officers logged, court heard during the opening statement.
In another, a suspect who was arrested with $10,000 cash and diamond earrings worth $20,000 shows no cash or jewelry on the official record, the prosecution said.
A charge of conspiracy among the officers, Pearson said, is the "bright thread that runs throughout the entire case" and goes as far as some of them perjuring themselves in court.
While several of the witnesses in the case are criminals who the jury may find unsavoury, Pearson said, he warned not to judge their testimony based on their past activities. He also promised to bring forward other police officers as well as records and documents to back up that testimony.
The case against John Schertzer, Ned Maodus, Steven Correia, Joseph Miched and Raymond Pollard goes back more than a decade, at the start of what ended up being a $14-million investigation into the conduct of members of the Toronto police drug squad.
Charges were first laid in 2004, but delays have slowed the case's progress through the courts.
The men have all pleaded not guilty and none of the allegations have been proven in court.
The trial is expected to last several months.